Electrically powered wheelchairs have a chassis to which a seating system is mounted. The seating system may comprise a seat frame to which the seat cushion is mounted, and a backrest frame mounted to the seat frame by means of a backrest fixation system. A backrest is mounted to the backrest frame. The backrest frame may for example comprise two vertical members which are attached to the seat frame, and to which the backrest is mounted.
Today, there are electrically powered wheelchairs on the market which have a seat frame arrangement that has one or more grooves along each lateral side, i.e. the wheel sides of the electrically powered wheelchair. These grooves may for example be used to attach various devices to the electrically powered wheelchair in a convenient manner. The grooves are sometimes also utilised for attaching the backrest fixation system by means of fasteners such as screws.
The assembly of such seat frame arrangements are rather difficult, because screw heads are inserted in the groove at the end face of the seat frame arrangement, where the groove opens. The screws then have to be assembled with the backrest frame, which is cumbersome.
When a wheelchair such as an electrically powered wheelchair is to be moved a greater distance it may be transported in a motor vehicle such as a bus or a car. The wheelchair occupant may occupy the wheelchair seat during such transport. In case of a large deceleration force, for example in the event of a crash, the force propagates to the backrest frame through the backrest fixation system. If the magnitude of the force reaches a threshold, shear stress acting on the fasteners may result in that the fasteners break, and/or in that the seat frame arrangement is damaged.